Exhaled nitric oxide stability over two years in relation to COPD outcomes

Area of Science:

• Pulmonology
• Respiratory Medicine
• Biomarkers

Background:

• Exhaled nitric oxide (FeNO) is a non-invasive biomarker used in asthma management.
• The clinical significance of FeNO in stable Chronic Obstructive Pulmonary Disease (COPD) remains less established.
• Previous studies show variable FeNO levels in COPD patients outside of exacerbations.

Purpose of the Study:

• To investigate the longitudinal stability of FeNO levels over two years in stable COPD subjects.
• To explore the relationship between FeNO levels, smoking status, lung function, and dyspnea in COPD.
• To assess the consistency of FeNO measurements for potential monitoring in stable COPD.

Main Methods:

• A two-year follow-up study of 353 COPD subjects from the TIE-study cohort.
• Three visits were conducted one year apart, measuring FeNO, lung function (FEV1%pred, FVC%pred), and dyspnea (mMRC).
• Subjects were categorized by smoking status (current smoker vs. ex-smoker) and FeNO levels (<20 ppb vs. ⩾20 ppb).

Main Results:

• Ex-smokers consistently exhibited higher FeNO50 values than current smokers across all visits (p<0.001).
• High consistency was observed, with 71-81% of participants remaining in their baseline FeNO group (low or high) after two years.
• Persistent low FeNO (<20 ppb) was associated with significantly lower FEV1%pred and FVC%pred, and higher reported dyspnea (mMRC ⩾ 2) among ex-smokers compared to the persistent high FeNO group.

Conclusions:

• FeNO measurements demonstrate good consistency over two years in stable COPD patients, supporting its potential as a monitoring tool.
• Persistent low FeNO levels in COPD are linked to worse lung function and increased symptom burden, particularly dyspnea.
• These findings highlight the clinical relevance of FeNO profiling in understanding COPD phenotypes and disease progression.